The Experts below are selected from a list of 61056 Experts worldwide ranked by ideXlab platform
Hilmi Volkan Demir - One of the best experts on this subject based on the ideXlab platform.
-
nonradiative energy transfer in a layered metal dielectric nanostructure mediated by surface plasmons
Proceedings of SPIE, 2015Co-Authors: Sepideh Golmakaniyoon, Hilmi Volkan DemirAbstract:Nonradiative energy transfer (NRET) has been applied in various applications of Nanosensors, Raman scattering, color tuning, light harvesting and organic light emitting structures. Due to the small range of donor-acceptor Separation Distance that NRET is effective, the improvement in energy transfer (ET) efficiency for thicker structures seems necessary. The plasmons resonance energy transfer (PRET) has been successfully employed to improve the NRET efficiency. The conventional plasmonic configuration consists of donor-metal nanostructure-acceptor shows remarkable improvement of PRET efficiency from the excited donor dipole to the acceptor molecule in longer Separation Distance. We report the first successful cascaded plasmons coupling in planar structure of donor/acceptor thin film that significantly gives rise to enhancement of ET efficiency. Moreover, the theoretical analysis shows an enhancement in induced electric field due to stratified metal-dielectric configuration compared to simple metal thin film. We observed ET efficiency increases more than 100% by applying dielectric layer between two metal films in plasmonic structure.
-
evidence for nonradiative energy transfer in graphene oxide based hybrid structures
Journal of Physical Chemistry C, 2013Co-Authors: Aydan Yeltik, Burak Guzelturk, Yusuf Kelestemur, Gokce Kucukayandogu, Somayeh Fardindoost, Hilmi Volkan DemirAbstract:Solution processed graphene variants including graphene oxide (GO) and reduced graphene oxide (RGO) are promising materials for potential optoelectronic applications. To date, efficiency of the excitation energy transfer into GO and RGO thin layers has not been investigated in terms of donor–acceptor Separation Distance. In the present work, we study nonradiative energy transfer (NRET) from CdSe/CdS quantum dots into single and/or double layer GO or RGO using time-resolved fluorescence spectroscopy. We observe shorter lifetimes as the Separation Distance between the QDs and GO or RGO decreases. In accordance with these lifetimes, the rates reveal the presence of two different mechanisms dominating the NRET. Here we show that excitonic NRET is predominant at longer intervals while both excitonic and nonexcitonic NRET exist at shorter Distances. In addition, we find the NRET rate behavior to be strongly dependent on the reduction degree of the GO-based layers. We obtain high NRET efficiency levels of ∼97 an...
Duysinx Pierre - One of the best experts on this subject based on the ideXlab platform.
-
Imposing minimum and maximum member size, minimum cavity size, and minimum Separation Distance between solid members in topology optimization
'Elsevier BV', 2020Co-Authors: Fernandez Sanchez, Eduardo Felipe, Yang Kai-ke, Koppen Stijn, Alarcon Soto Pablo, Bauduin Simon, Duysinx PierreAbstract:peer reviewedaudience: popularizationThis paper focuses on density-based topology optimization and proposes a combined method to simultaneously impose Minimum length scale in the Solid phase (MinSolid), Minimum length scale in the Void phase (MinVoid) and Maximum length scale in the Solid phase (MaxSolid). MinSolid and MinVoid mean that the size of solid parts and cavities must be greater than the size of a prescribed circle or sphere. This is ensured through the robust design approach based on eroded, intermediate and dilated designs. MaxSolid seeks to restrict the formation of solid parts larger than a prescribed size, which is imposed through local volume restrictions. In the first part of this article, we show that by proportionally restricting the maximum size of the eroded, intermediate and dilated designs, it is possible to obtain optimized designs satisfying, simultaneously, MinSolid, MinVoid and MaxSolid. However, in spite of obtaining designs with crisp boundaries, some results can be difficult to manufacture due to the presence of multiple rounded cavities, which are introduced by the maximum size restriction with the sole purpose of avoiding thick solid members in the structure. To address this issue, in the second part of this article we propose a new geometric constraint that seeks to control the minimum Separation Distance between two solid members, also called the Minimum Gap (MinGap). Differently from MinVoid, MinGap introduces large void areas that do not necessarily have to be round. 2D and 3D test cases show that simultaneous control of MinSolid, MinVoid, MaxSolid and MinGap can be useful to improve the manufacturability of maximum size constrained designs.Aero+ Projec
-
Imposing minimum and maximum member size, minimum cavity size, and minimum Separation Distance between solid members in topology optimization
2020Co-Authors: Fernandez Sanchez, Eduardo Felipe, Yang Kai-ke, Koppen Stijn, Alarcon Soto Pablo, Bauduin Simon, Duysinx PierreAbstract:This paper focuses on density-based topology optimization and proposes a combined method to simultaneously impose Minimum length scale in the Solid phase (MinSolid), Minimum length scale in the Void phase (MinVoid) and Maximum length scale in the Solid phase (MaxSolid). MinSolid and MinVoid mean that the size of solid parts and cavities must be greater than the size of a prescribed circle or sphere. This is ensured through the robust design approach based on eroded, intermediate and dilated designs. MaxSolid seeks to restrict the formation of solid parts larger than a prescribed size, which is imposed through local volume restrictions. In the first part of this article, we show that by proportionally restricting the maximum size of the eroded, intermediate and dilated designs, it is possible to obtain optimized designs satisfying, simultaneously, MinSolid, MinVoid and MaxSolid. However, in spite of obtaining designs with crisp boundaries, some results can be difficult to manufacture due to the presence of multiple rounded cavities, which are introduced by the maximum size restriction with the sole purpose of avoiding thick solid members in the structure. To address this issue, in the second part of this article we propose a new geometric constraint that seeks to control the minimum Separation Distance between two solid members, also called the Minimum Gap (MinGap). Differently from MinVoid, MinGap introduces large void areas that do not necessarily have to be round. 2D and 3D test cases show that simultaneous control of MinSolid, MinVoid, MaxSolid and MinGap can be useful to improve the manufacturability of maximum size constrained designs.Peer reviewe
Kun Zhao - One of the best experts on this subject based on the ideXlab platform.
-
experimental and theoretical study on downward flame spread over uninhibited pmma slabs under different pressure environments
Applied Thermal Engineering, 2018Co-Authors: Kun Zhao, Xiaodong Zhou, Wei Tang, Michael J Gollner, Fei Peng, Lizhong YangAbstract:Abstract This paper presents an experimental and theoretical study of side-edge effects on downward flame spread over two parallel polymethyl methacrylate (PMMA) slabs under different pressure environments. Identical experiments of downward flame spread over thin PMMA slabs with side-edges unrestrained were conducted at different altitudes in Hefei (102 kPa), Geermu (73.2 kPa) and Lhasa (66.3 kPa). Experimental results show that the flame spread rate is controlled by ignition along the side-edge, rather than at the center of the samples, for experiments with both single and two parallel slabs. Based on these results, a thermal model is developed which describes flame spread along the edge and quantitatively agrees with experimental results. In the parallel-slab case, convective heating appears to influence the spread rate only when the Separation Distance is very small, with radiative heating playing a more important role as Separation Distance increases. The angle of the pyrolysis front, formed between the faster side-edge spread and slower center-region spread, hardly changes with pressure, but changes significantly with Separation Distance, due to differing modes of heat transfer between the side-edge and center region. In addition, variations of flame height with pressure and Separation Distance are reasonably interpreted from diffusion flame theory.
Jianfeng Meng - One of the best experts on this subject based on the ideXlab platform.
-
material removal mechanism and crack propagation in single scratch and double scratch tests of single crystal silicon carbide by abrasives on wire saw
Ceramics International, 2019Co-Authors: Peizhi Wang, Jianfeng MengAbstract:Abstract Single-crystal silicon carbide is a promising semiconductor material widely applied in micro-electronics. However, its high hardness and brittleness make it difficult to be sliced into wafers by wire sawing technology. In this paper, both single scratch and double scratch tests are carried out on the (0001) surface of 4H-SiC by the abrasives on wire saw instead of using a standard indenter to obtain an in-depth understanding of the material removal mechanism and crack propagation in wire sawing. The scratching groove in single scratch tests is found to be composed of several small grooves because of the actual irregular shape of the abrasive. Stress analysis shows that this phenomenon has relatively small effects on the radial cracks propagating near the { 1 1 ¯ 00 } primary cleavage plane. Radial cracks play an important role in the process of material removal by means of the interaction between radial cracks and the interaction between radial cracks and lateral cracks in double scratch tests. Based on fracture mechanics, the variation of stress intensity factors (SIFs) at the tip of radial cracks with the Separation Distance between the two grooves is calculated. Results show that the values of SIFs increase with the decrease of the Separation Distance, which means that radial cracks are more easily to propagate when the Separation Distance decreases. The theoretical analysis agrees with the experimental observation.
Fernandez Sanchez, Eduardo Felipe - One of the best experts on this subject based on the ideXlab platform.
-
Imposing minimum and maximum member size, minimum cavity size, and minimum Separation Distance between solid members in topology optimization
'Elsevier BV', 2020Co-Authors: Fernandez Sanchez, Eduardo Felipe, Yang Kai-ke, Koppen Stijn, Alarcon Soto Pablo, Bauduin Simon, Duysinx PierreAbstract:peer reviewedaudience: popularizationThis paper focuses on density-based topology optimization and proposes a combined method to simultaneously impose Minimum length scale in the Solid phase (MinSolid), Minimum length scale in the Void phase (MinVoid) and Maximum length scale in the Solid phase (MaxSolid). MinSolid and MinVoid mean that the size of solid parts and cavities must be greater than the size of a prescribed circle or sphere. This is ensured through the robust design approach based on eroded, intermediate and dilated designs. MaxSolid seeks to restrict the formation of solid parts larger than a prescribed size, which is imposed through local volume restrictions. In the first part of this article, we show that by proportionally restricting the maximum size of the eroded, intermediate and dilated designs, it is possible to obtain optimized designs satisfying, simultaneously, MinSolid, MinVoid and MaxSolid. However, in spite of obtaining designs with crisp boundaries, some results can be difficult to manufacture due to the presence of multiple rounded cavities, which are introduced by the maximum size restriction with the sole purpose of avoiding thick solid members in the structure. To address this issue, in the second part of this article we propose a new geometric constraint that seeks to control the minimum Separation Distance between two solid members, also called the Minimum Gap (MinGap). Differently from MinVoid, MinGap introduces large void areas that do not necessarily have to be round. 2D and 3D test cases show that simultaneous control of MinSolid, MinVoid, MaxSolid and MinGap can be useful to improve the manufacturability of maximum size constrained designs.Aero+ Projec
-
Imposing minimum and maximum member size, minimum cavity size, and minimum Separation Distance between solid members in topology optimization
2020Co-Authors: Fernandez Sanchez, Eduardo Felipe, Yang Kai-ke, Koppen Stijn, Alarcon Soto Pablo, Bauduin Simon, Duysinx PierreAbstract:This paper focuses on density-based topology optimization and proposes a combined method to simultaneously impose Minimum length scale in the Solid phase (MinSolid), Minimum length scale in the Void phase (MinVoid) and Maximum length scale in the Solid phase (MaxSolid). MinSolid and MinVoid mean that the size of solid parts and cavities must be greater than the size of a prescribed circle or sphere. This is ensured through the robust design approach based on eroded, intermediate and dilated designs. MaxSolid seeks to restrict the formation of solid parts larger than a prescribed size, which is imposed through local volume restrictions. In the first part of this article, we show that by proportionally restricting the maximum size of the eroded, intermediate and dilated designs, it is possible to obtain optimized designs satisfying, simultaneously, MinSolid, MinVoid and MaxSolid. However, in spite of obtaining designs with crisp boundaries, some results can be difficult to manufacture due to the presence of multiple rounded cavities, which are introduced by the maximum size restriction with the sole purpose of avoiding thick solid members in the structure. To address this issue, in the second part of this article we propose a new geometric constraint that seeks to control the minimum Separation Distance between two solid members, also called the Minimum Gap (MinGap). Differently from MinVoid, MinGap introduces large void areas that do not necessarily have to be round. 2D and 3D test cases show that simultaneous control of MinSolid, MinVoid, MaxSolid and MinGap can be useful to improve the manufacturability of maximum size constrained designs.Peer reviewe
